Poly(vinyl butyral) (PVB) is commonly used in the manufacture of polymer layers that can be used as interlayers in light-transmitting laminates such as safety glass or polymeric laminates. Safety glass often refers to a transparent laminate comprising a poly(vinyl butyral) layer disposed between two layers of glass. Safety glass often is used to provide a transparent barrier in architectural and automotive openings. Its main function is to absorb energy, such as that caused by a blow from an object, without allowing penetration through the opening or the dispersion of shards of glass, thus minimizing damage or injury to the objects or persons within an enclosed area. Safety glass also can be used to provide other beneficial effects, such as to attenuate acoustic noise, reduce UV and/or IR light transmission, and/or enhance the appearance and aesthetic appeal of window openings.
In automobiles and some architectural applications of multiple layer laminated safety glass, or multiple layer glazings, there exists a desire to heat the glass, to, for example, allow for the defrosting of the glass. Such defrosting can be accomplished by, for example, using Tungsten or Wolfram wires stitched onto a polymer layer that is then laminated between two layers of glass to form a rear window. Another conventional approach uses a very thin metal layer applied to glass in a laminated glass assembly. In either case, an electrical potential is applied across the conductor and the resistance to the resultant current produces heat.
While the above-cited methods are effective at defrosting the multiple layer glazing in which the conductive components are included, they can present difficulties in manufacture. Further, defrosters exposed to the environment, such as surface-applied conductive lines on a glass laminate, can be mechanically damaged, resulting in loss of function. Conventional defrosters, as described above, also tend to either provide less functionality than desired or a greater degree of visual contamination than desired.
What are needed in the art are improved multiple layer glazing constructs that provide easy and inexpensive fabrication and that provide ready defrosting or heating in the finished application.